(1.) Field of the Invention
The present invention relates to a system for controlling the throttling of intake air and the pressure of fuel injection in a diesel engine.
(2.) Description of the Related Art
Diesel engines are conventionally provided with mechanisms for throttling intake air so as to reduce engine vibration and noise to acceptable levels in a light load condition. Throttling of intake air, however, can have a detrimental effect on the combustion of fuel by the engines.
In diesel engines, the effectiveness of fuel combustion is governed by the conditions of fuel spray, e.g., the force of penetration of the fuel, the degree of atomization of the fuel, and the degree of mixing with the vortical air stream (swirl) in the combustion chamber. These are in turn determined by the fuel injection pressure, the swirl strength, and the position of the injection hole.
While the strength of the swirl is dependent upon the engine speed, it particularly declines upon throttling of the intake air. As a result, an increased amount of fuel strikes or adheres to the walls of the engine combustion chamber, preventing proper mixture with the air. This, as mentioned above, has a detrimental effect on the combustion of the fuel and results in increased emission of hydrocarbons and carbon monoxide and increased emission of white smoke.